The use of LED (light emitting diode) light sources including a plurality of LEDs, or laser light sources including a plurality of laser emitting elements, in place of high pressure mercury lamps or xenon lamps as light sources for projection display devices has recently been proposed.
There is, however, a problem that the temperature dependency of red laser emitting elements, for example, is high, requiring control by a Peltier element or the like, so the cooling mechanism becomes complex. Another problem is that small green laser emitting elements with high output are unavailable. From these problems have come proposals for light source devices using phosphors.
Patent reference 1 discloses a light source device in which excitation light excites a phosphor, and the excited phosphor outputs light (output light) in a certain wavelength band when it returns to its ground state. The excitation light radiated from the excitation light source irradiates a phosphor wheel. The phosphor wheel has a segment area with a phosphor layer that emits light in a red wavelength band, a segment area with a phosphor layer that emits light in a green wavelength band, and a segment area with a phosphor layer that emits light in a blue wavelength band. LEDs or laser emitting elements are used as the excitation light source. A wheel motor spins the phosphor wheel so that the excitation light excites the phosphor of the color in each segment area in turn. Patent reference 1 proposes a light source device that outputs output light of each color (light in the wavelength band of each color) in turn.